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Mr. Harland Knoll San Joaquin County Environmental Health Department December 28, 2004 • Page 2 of 3 Groundwater Sampling and Analytical Results Groundwater monitoring wells MW-1 through MW-3 was sampled on October 12, 2004. The methods used to collect the samples are presented in Attachment A. Samples from these wells were analyzed for total petroleum hydrocarbons in the gasoline range (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), methyl tertiary butyl ether (MTBE), tertiary amyl methyl ether(TAME), tertiary butyl alcohol (TBA), di-isopropyl ether(DIPS), and ethyl tertiary butyl ether (ETBE) using EPA Test Method 826013, and total petroleum hydrocarbons as diesel (TPHd) using EPA Test Method 8015 modified.. Kiff Analytical Labs, Inc. (Kiff Analytical) of Davis, California, a California state-certified laboratory, performed the chemical analyses. The analytical laboratory report, including chain-of-custody documentation, is included as Enclosure C. Laboratory analyses results for the fourth quarter 2004 sampling event are presented in Table 2 and concentrations of MTBE, benzene, TPHg, and TPHd are shown on Figure 3. Conclusions • Concentrations of TPHg increased in MW-1 and MW-2, to 140 and 120 micrograms per liter (4g/L),respectively. • Concentrations of TPHd decreased in MW-1 and MW-2, to X50 and 60 µg/L,respectively • Concentrations of MTBE in groundwater decreased by an order of magnitude in MW-1 (Table 2). ■ The groundwater flow direction trend continues to be to the south, with a more westerly component evident during the last two quarters (Figure 4). ■ Groundwater gradient is the highest recorded at 0.018 feet per foot(previous high of 0.003). Future Work The next groundwater monitoring event is scheduled for January 2004. Remarks The recommendations contained in this report represent Delta's professional opinions based upon the currently available information and are arrived at in accordance with currently acceptable professional standards. This report is based upon a specific scope of work requested by the client. The contract between Delta and its client outlines the scope of work, and only those tasks specifically authorized by the contract or outlined in this report were performed. This report is intended only for the use of Delta's client and anyone else specifically listed on this report. Delta will not and cannot be liable for unauthorized reliance by any other third party. Other than as contained in this paragraph, Delta makes no express or limited warranty as to the contents of this report.